A demonstration of subcellular resolution capability is proposed, using 1.2 MeV protons capable of penetrating erythrocytes and other cells in straight lines, and of measuring intracellular distributions of trace elements by the proton-induced X-ray (PIXE) technique. Existing equipment will be used, composed of a van de Graaff accelerator, objective slits, aperture slits, microbeam lens of achromatic design, and specimen chamber with installed detectors. Resolution is measured by counting secondary electrons generated as the beam is swept across the edge of a fine carbon filament. With improved vacuum between the objective slits and the lens, a resolution of 0.2 microns is expected.